The present invention relates to a conversion set for a portable circular saw according to the preamble of claim 1.
Portable circular saws of the usual type, for example applicant's Kress saw model 6050/55 which is particularly well suited for the purposes of the present invention, comprise a housing accommodating an electric drive motor and in some cases also the latter's gear. The power of the electric motor of such saws is relatively high, compared with other usual electric hand tools, for example in the range of 1 kW. The housing comprises further handles for guiding the portable hand saw, the longitudinal axis of the driving electric motor extending transversely to the cutting direction of the portable hand saw so that the circular saw blade can be mounted on the output shaft end to rotate therewith and can be secured thereon in a suitable manner, usually by a locking screw of suitable shape and structure, without the use of a direction-change gear. The overall shape of such a portable circular saw normally tapers in downward direction and ends in a foot or base which can be adjusted as regards its distance to the housing whereby the cutting depth of the portable circular saw is varied--this adjustment being normally made on one side only--and which in addition can be inclined at pre-determined angles so as to permit the execution of angular cuts. In addition, it is possible by means of the foot or corresponding guide means provided on the housing to use different rip fences so that defined cuts are rendered possible. Portable circular saws of this type are suited for sawing boards or the like it being however rarely possible to achieve a cutting depth in excess of 20 to maximally 30 mm.
On the other hand, there are known in the art chain saws of many shapes and designs, for example in the form of power saws driven by a combustion engine or in the form of electric chain saws which provide the combined advantage of smoother operation and easier handling so that such electric chain saws have found acceptance not only in industrial applications, but also, and in particular, in the private area, for example for preparing firewood, for cutting larger trees, and the like.
For converting electric hand tools for different applications a great number of adapter systems, and the like, have been known. According to one of these systems, a motor of a given power is equipped with a suitable mounting surface which can be attached to, for example clicked in place on, different tool attachments or adapter arrangements so that a plurality of individual tools can be driven by a single electric motor.
The possibility to convert a portable circular saw into an electric chain saw has never been seen before, and this in the first line because a portable circular saw comprises a plurality of safety features, mainly due to the relatively high risk of injuries connected with its handling, for example a full-size rigid upper blade guard fixed to the housing and an additional pivoting safety guard which covers the lower part of the saw blade in its inoperative position and is progressively pivoted to the rear as the saw advances through the material to be cut. In addition, electric chain saws differ considerably from portable circular saws as regards their basic shape. An electric chain saw comprises, for example, a guide bar projecting horizontally and transversely from its forward end and serving as a guide for the chain. In the case of a portable circular saw, this area is provided with a full-size and rigid enclosure so that a conversion between these two types of saws would seem impossible already for this reason. When tools are to be converted, i.e. changed over from one form to another form, one has to consider in addition that the required conversion work must not be too complicated for private people because otherwise they would rather not use the conversion set and, in the present case, not use a dual-saws chain saw, but prefer to do completely without the chain saw attachment or to use two separate systems, at considerably higher cost. Also, it is of importance in this connection that the machine obtained after conversion must not be too different from the usual form of such a machine, in the present case a chain saw, and must be fully serviceable while meeting at least the same safety standards as other electric chain saws.
Now, it is the novel object of the present invention to provide a conversion set for a portable circular saw which permits the latter to be converted with the least possible effort into an electric chain saw with perfect and precise handling properties.